Cytochrome model compounds

Catalysis. Cytochrome P-450 model compounds catalyze the epoxidation of alkenes by hypochlorite ions.16 A typical catalyst is OMn(TMP)L+. 

These researchers also described [93] the design and synthesis of iron(II) porphyrin dendrimers with triethylene glycol monomethyl, ether surface groups (e.g., 31) which render them soluble in a wide range of organic solvents and water. The potential difference between the first (1 FeCl) and second generation (2 FeCl) Fe-porphryin dendrimers was found to increase more in water than in dichloromethane (0.42 vs 0.08 V). This remarkable potential difference between 2 FeCl and 1 FeCl in water was comparable with that found between cytochrome c and a similarly ligated, more solvent-exposed cytochrome c heme model compound. 

S.3 Cytochrome P450 Model Compounds Functional. Ferric-peroxo species are part of the cytochrome P450 catalytic cycle as discussed previously in Section 7.4.4. For instance, these ferric-peroxo moieties are known to act as nucleophiles attacking aldehydic carbon atoms in oxidative deformylations to produce aromatic species.An example of this work, establishing the nucleophilic nature of [(porphyrin)Fe (02)] complexes, was achieved for alkene epoxidation reactions by J. S. Valentine and co-workers. The electron-deficient compound menadione (see Figure 7.18) yielded menadione epoxide when reacted with a [(porphyrin)Fe X02)] complex. 

Figure 7.22 Cytochrome P450 model compound reaction profile consistent with a multi-step catalytic mechanism. (Adapted with permission from Schemes 7 and 8 of reference 68. Copyright 1997, Society of Biological Inorganic Chemistry.)...

Cytochrome c Oxidase Model Compounds and Associated Analytical Techniques... 

In 2004, Kenneth Karlin and co-workers published an extensive review of cytochrome c oxidase model compounds. Hundreds of CcO models exist, with more being synthesized and studied into the current time. These can be broken down into a number of categories as Karlin s group does in the 2004... 

Finally, in this section we discuss the model compounds for the Type III binuclear Cua center. Electron transfer (eT) to and from Cua is remarkably fast, considering the distances to be traveled. Intermolecular eT from cytochrome c Cua, over a distance of -18-20 A, has a rate constant, k, equal to 6 X ICf s while intramolecular eT from Cua heme a, also over an -18- to 20-A distance, has a rate constant of 1 x lO s The Cua center exists in two redox states the reduced form with two cuprous ions (Cu -Cu ) and the fully delocalized mixed valent center (Cu -Cu Cu -Cu =Cu - -Cu ). In the... 

Figure 7.48 Two cytochrome c oxidase Cua center model compounds (A) delocalized core with two i-l,3-(KN KO)-ureate bridges as reported in reference 165-and (B) a dithiolate-bridged mixed-valence binuclear copper ion complex as re in reference 166.

A novel cytochrome b model compound containing two heme binding sites was tested by EPR and Mossbauer spectroscopy. Both sites were found to be occupied in a 1 1 stoichiometry. For one of the sites a normal b-hemichrome EPR signal with rhombic -tensor symmetry was found as expected for a bis-histidine ligation with parallel histidine planes. For the other site unusual EPR features (e.g. axial y-tensor) were obtained which were ascribed to a configuration with perpendicular histidine planes.267 A new type of cytochrome b was described for a preparation from the cytoplasmic fraction of an archaeon, Acidianus ambivalens. This is thus the first soluble cytochrome found in this... 

Fig. 4. Structure of 7, a model compound for the 02 complex of cytochrome P450 6...

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